1. Field
The present invention relates to elevators, methods for forming elevators, uses of auxiliary forces in elevators.
2. Description of Related Art
One of the objectives in elevator development work is to achieve an efficient and economical utilization of building space. In recent years, this development work has produced various elevator solutions without machine room, among other things. Good examples of elevators without machine room are disclosed in specifications EP 0 631 967 (A1) and EP 0 631 968. The elevators described in these specifications are fairly efficient in respect of space utilization as they have made it possible to eliminate the space required by the elevator machine room in the building without a need to enlarge the elevator shaft. In the elevators disclosed in these specifications, the machine is compact at least in one direction, but in other directions it may have much larger dimensions than a conventional elevator machine.
In these basically good elevator solutions, the space required by and placement of the hoisting machine limits the freedom of choice in elevator lay-out solutions. Some space is needed to provide for the passage of the hoisting ropes. It is difficult to reduce the space required by the elevator car itself on its track and likewise the space required by the counterweight, at least at a reasonable cost and without impairing the performance and operational quality of the elevator. In the case of a traction sheave elevator without machine room, mounting the hoisting machine in the elevator shaft is difficult, especially in a solution with machine above, because the hoisting machine is an object of fairly large size and weight. Especially in the case of larger loads, speeds and/or hoisting heights, the size and weight of the machine are a problem regarding installation, even so much so that the required machine size and weight have in practice limited the sphere of application of the concept of elevator without machine room or at least retarded the introduction of said concept in larger elevators. In modernization of elevators, the space available in the elevator shaft has often limited the sphere of application of the concept of elevator without machine room. Often, especially when hydraulic elevators have had to be modernized or replaced, it has not been practical to apply a roped elevator solution without machine room due to insufficient space in the elevator shaft, particularly when no counterweight has been used in the hydraulic elevator solution to be modernized/replaced. The drawbacks of elevators with counterweight are the cost of the counterweight and the space required for the counterweight in the elevator shaft. Drum driven elevators, which are nowadays rather seldom installed, have the drawbacks of heavy and complicated hoisting machines and their large power and/or torque requirement. Prior-art elevators without counterweight are exotic. So far it has not been technically or economically reasonable to make elevators without counterweight. One solution like this is disclosed in specification WO9806655. A recent international patent application discloses a feasible solution. In prior-art elevator solutions without counterweight, the tensioning of the hoisting rope is implemented using a weight or spring, and that is not an attractive approach to implementing the tensioning of the hoisting rope. Another problem with elevators without counterweight, when long ropes are used e.g. due to a large hoisting height or large suspension ratios used, is the compensation of rope elongations, and a further problem is how to maintain a sufficient friction between the traction sheave and the hoisting ropes. An additional problem is how to ensure the compensation and/or equalization of rope elongations and/or rope tensions, and/or how to ensure the reliability of the compensating device used. In an elevator, especially an elevator without counterweight, a further problem is uncontrolled slackening of the hoisting ropes and the risk of the ropes getting tangled in a disturbance situation.